This invention relates generally to an electrical wiring support assembly and, more particularly, to such an assembly adapted for use in installing electrical wiring in a building particularly for low voltage applications.
Currently, electrical wiring is installed through open areas in building structures by first drilling holes through wooden frame elements such as studs (upright wall supports), joists (long horizontal supports that floor boards or ceiling laths are fastened to), stringers (long horizontal supports) and rafters (sloping roof beams). Wiring is then passed through the drilled holes. This process is time consuming, requires the use of a drill, and weakens the support members that must be drilled-through.
Another common method for supporting wiring in a horizontal orientation within a building without having to drill holes in support members is to simply lay the wiring across the stringers and/or joists that form the unimproved xe2x80x9cfloorxe2x80x9d of an attic. However, attic wiring is often subjected to extreme high and/or low temperatures and may be subjected to substantial temperature swings according to seasonal temperature variations experienced in most parts of the world. Temperature extremes and/or substantial temperature variations of this kind can shorten the life of materials used to insulate electrical wiring. Temperature variations also complicate the wiring design of a building by changing the ampacity ratings of wire conductors. In addition, it is hazardous for workers to attempt to service wiring that is supported in this way. Servicing attic wiring is hazardous because, to reach the wires, workers must sometimes attempt to walk across and stand on unimproved attic flooring, i.e., stringers or floor joists with no actual floorboards covering them.
To facilitate the suspension of electrical wiring in buildings in general and the horizontal suspension of electrical wiring in particular, various types of support apparatus in the form of duct, channel, hanger or conduit systems are employed. Such suspension means allow installers to route and support wires beneath frame structures such as ceiling joists and stringers that are disposed above inhabited, temperature-controlled areas of a buildingxe2x80x94areas that service personnel can more readily gain access to.
One example of such a system is disclosed in U.S. Pat. No. 2,917,083 issued Dec. 15, 1959 to Duvall et al. The Duvall et al. system includes a fully enclosed duct used in commercial construction to support electrical wires. A generally rectangular-shaped coupler connects lengths of the duct end-to-end. Duvall et al. also discloses a duct hanger having a fastening flange with holes through which fasteners such as nails may be driven into an external support structure such as a wooden joist or stringer. The system also includes an end-cap section for closing-off the open end of a duct. Each of the above components of the Duvall et al. system is made of sheet metalxe2x80x94a material that can be expensive and difficult to form and that can present problems in electrical wiring applications due to its high conductivity and characteristically sharp edges. In addition the hangers are two-piece L-shaped units that are relatively difficult to install, as they must be fastened together and to the duct using separate fastening hardware. The couplers are also relatively difficult to install and are also difficult to construct. The couplers are difficult to construct because they must be cut or stamped from sheet metal in two pieces then joined together at a hinged connection. The couplers are difficult to install because they must be fastened within and between two lengths of duct by separate fastening hardware. Still further, these hangers are limited in that they must be positioned at joints between duct lengths to engage studs also used to connect the couplers to the duct ends. In addition, because a completely enclosed duct supports the wiring, the system cannot be used to route certain types of nonmetallic sheathed cable without violating Article 336 of the National Fire Protection Association (NFPA) National Electrical Code. Specifically, types NM and NMC nonmetallic sheathed cable may not be supported within enclosed ducting. Unfortunately, NM-type cable is very common in residential home construction.
Another example of such a system is disclosed in U.S. Pat. No. 1,992,574 issued Feb. 26, 1935 to Jenkins. Similar to the Duvall et al. system, the Jenkins system includes fully enclosed duct sections with box-shaped cross-sections used in commercial construction to support electrical wires. Couplers in the form of end flanges integrally formed at the ends of each length of the duct are configured to join duct sections. Jenkins also discloses a duct hanger with a generally rectangular frame section and an integral fastening flange with holes through which fasteners such as nails may be driven into an external support structure. The system also includes an end-cap section for closing-off the open end of a duct. As with the Duvall et al. system, each of the above components is made of sheet metal and therefore has all the same attendant limitations. The Jenkins hangers are single piece units but must be fastened to end-flange portions of the ducts using separate fastening hardware. The coupler flanges make the duct forming process more difficult as they extend integrally outward from the ends of the ducts. To couple separate lengths of duct the end flanges are fastened together using separate fastening hardware. In addition, the hangers must be assembled to the duct at the same time as the duct lengths are being joined together. This is because the hangers must be positioned between the end flanges and are held in place by the same fastening hardware that joins the end flanges together. As with the Duvall et al. system, the fully enclosed duct of the Jenkins system makes it incompatible with certain non-metallic sheathed cable.
Because of the inherent problems associated with using metal components to support electrical wiring, some current systems include wire suspension components made of plastic. One such system is disclosed in U.S. Pat. No. 4,857,670, issued Aug. 15, 1989 to Frank et al. Frank et al. discloses fully enclosed PVC duct sections for supporting electrical wiring. Couplers in the form of tabs join the duct sections together end-to-end. Opposite ends of each tab are slidably received into grooves formed within each end of each duct section. The tabs and grooves are configured to join duct sections end-to-end in either linear fashion or at right angles. The duct sections include an integrally hinged cover that snaps into place over a U-shaped trough to form the fully enclosed duct with a generally rectangular cross-section. The grooves, the hinged cover and the snap-fit connection of each duct section are relatively complex and difficult to extrude or mold. In addition, the Frank et al. system has the same incompatibility problem with certain types of non-metallic sheathed cable as do the Duvall et al. and Jenkins systems.
What is needed is an electrical wiring support assembly that is inexpensive to manufacture and easy to assemble and install without weakening building structures. What is also needed is such an assembly that can be used with types NM and NMC non-metallic sheathed cable without violating the NFPA National Electrical Code. Also needed is such an assembly that does not create or increase the risk of short-circuiting the electrical wires that it supports. In particular, such assemblies are needed for low voltage applications.
In accordance with this invention an electrical wire support assembly for supporting electrical wire on building interior structures is provided that comprises a hanger configured to support low voltage electrical wires. The hanger includes a frame section and a fastening flange connected to the frame section. The frame section is configured to support low voltage electrical wires and an elongated cover section that conceals low voltage electrical wires supported on the hanger. The fastening flange is configured to secure the hanger to a building interior structure.
According to another aspect of the invention the cover section is configured to fit over the hanger frame section. This configuration allows an installer to snap the cover into place after installing the hanger and running the wire through the hanger.
According to another aspect of the invention the cover section has a generally U-shaped cross-section. The U-shaped cross section defines an elongated inner channel. The frame section of the hanger is disposed in the inner channel of the cover section.
According to another aspect of the invention the assembly includes at least one additional elongated cover section. The assembly also includes at least one additional hanger and at least one coupler configured to join the abutting ends of two cover sections together in an end-to-end disposition.
According to another aspect of the invention each coupler comprises a collar configured to receive and join the abutting ends of two adjacent cover sections. This exterior collar configuration allows an installer to fit the collars into place over abutted ends of cover sections that have already been installed over the hanger frame sections and positioned end-to-end along the wiring path.
According to another aspect of the invention each coupler has a generally C-shaped cross-section slightly larger than that of the cover sections. The slightly larger cross-section allows the couplers to fit around the abutted ends of the cover sections.
According to another aspect of the invention each coupler includes a pair of parallel coupler side walls that extend integrally and generally perpendicularly upward from a coupler base. Each coupler side wall has an upper edge. A projection of a first pair of projections extend integrally and generally perpendicularly inward from the respective end wall upper edges to respective inner ends of the first pair of projections. Each projection of the first pair of projections extends over and engages a cover side wall upper edge, preventing the cover section ends from lifting out of the coupler. The first projection inner ends are spaced apart to define an upper coupler opening.
According to another aspect of the invention each coupler includes a second pair of projections extending integrally and generally perpendicularly downward from respective inner ends of the first pair of projections. The downward projections further secure the coupler to the cover side wall upper edges.
According to another aspect of the invention each hanger includes a horizontal ridge that extends integrally outwardly from along a portion of the frame section of each hanger. The inner channel of each cover section includes a longitudinal groove that is shaped and positioned to receive the frame section ridges. The ridges and channels cooperate to allow the cover sections to be fitted into position over the hanger frame sections.
According to another aspect of the invention the U-shaped cross-section of each cover section has generally parallel cover side walls that extend generally perpendicularly upward from a cover base. Upper edges of the side walls define a longitudinal upper opening in each cover section. The cover grooves are disposed in and along respective opposite inner side surfaces of the respective opposite cover side walls. Each hanger frame section has generally parallel frame side walls that extend generally perpendicularly between parallel upper and lower frame walls to form a generally rectangular shape. The horizontal longitudinal ridges extend integrally outwardly from along respective outer surfaces of the respective frame side walls. The frame side walls and ridges are positioned to engage the respective cover side walls and grooves. The lower frame wall is positioned to engage the cover base. Each coupler has a generally rectangular aperture shaped to receive abutting cover section ends.
According to another aspect of the invention the assembly includes at least one end-cap configured to attach to an end of a cover section and close-off an end of the cover channel.
According to another aspect of the invention each end-cap includes a pair of tabs engageable with the distal ends of respective elongated grooves of a cover section.
According to another aspect of the invention the frame section and fastening flange section of the hanger are integrally formed as a single unitary piece.
According to another aspect of the invention at least one hole extends through a thickness of the fastening flange. The holes are included to receive fasteners such as nails or screws used to attach the hanger to interior building structures.
According to another aspect of the invention the coupler, hanger and end cap maybe made of plastic. The use of plastic reduces the risk of electrical short circuits and damage to electrical insulation from sharp metal edges.
According to another aspect of the invention a method is provided for installing an electrical wire support assembly on building interior structures. The method includes the steps of attaching the fastening flange of a hanger to a building interior structural member along a desired electrical wiring path. Low voltage electrical wiring is then passed-through and supported within the hanger frame section and the cover section is engaged onto the hanger frame section.
According to another aspect of the invention the above method includes the provision of at least one additional hanger, cover section and coupler. The fastening flanges of the additional hangers are attached to building interior structural members at spaced points along the electrical wiring path. The fastening flanges of the additional hangers are attached to building interior structural members at spaced points along the low voltage electrical wiring path. The low voltage electrical wire is then passed-through and supported in the additional hanger frame section. The cover sections are then engaged onto the hanger frame sections and are joined by providing the couplers over the abutted ends of the cover sections.